With widespread proliferation of video distribution via internet, boards used as servers or routers have increasing channel capacities. To meet this, there have been increasingly studied techniques of replacing part of high-speed signal lines from an electric wiring to an optical wiring. Polymer optical waveguides are expected as optical wiring for photoelectric hybrid boards because of being available at lower cost than that of quartz optical waveguides. One of required properties of such polymer optical waveguides is thermal stability upon solder reflow (solder reflow thermal stability), which prevents thermal degradation such as increased optical loss and cracking caused by a high temperature treatment in a solder reflow process. In recent years, the polymer optical waveguides require more satisfactory thermal stability. This is because a higher reflow temperature is required to meet the use of lead-free solder whose melting requires heating at a high temperature of about 260° C.
In addition, the polymer optical waveguides also require flexibility from the viewpoints of easy binding with elements or substrates, degree of freedom in the layout, stress relaxation, and handleability. Specifically, polymers for use as polymer optical waveguides require excellent flexibility and satisfactory thermal stability even at temperatures higher than 260° C.
Patent Literature (PTL) 1 and PTL 2 disclose 3-ethyl-3-(meth)acryloyloxymethyloxetane and other compounds having an oxetane ring and a (meth)acryloyl group per one molecule. However, these compounds give cured products which have poor flexibility although they have satisfactory thermal stability.
PTL 3 and PTL 4 disclose glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and other epoxy compounds having an epoxy group and a (meth)acryloyl group per one molecule. However, these compounds have poor curability, have skin irritation and toxicity, and are thereby problematic in workability. In addition, these compounds give cured products which do not have sufficiently satisfactory flexibility. As is described above, there has not yet been found a resin capable of forming a cured product which excels both in flexibility and thermal stability.